1. Field of the Invention
The present invention relates generally to global positioning systems, and more specifically to a method and system for displaying maps for personal navigational aid.
2. Description of the Related Art
The global positioning system, or GPS, has recently been used extensively for application to wireless mobile terminals to serve as a personal navigational aid. According to the current method, the mobile terminal receives signals from GPS satellites, determines its global position by processing the received signals, and transmits a request via a mobile communications network to a map server for a map. The request contains information about the mobile""s global position and the scale of the map that is being requested (i.e. the size of the geographical area to be displayed). In response, the map server produces a map of the requested scale and communicates the map to the mobile terminal for display. However, due to the presence of hindrances in the paths of signals from line-of-sight GPS satellites, the received signals may be disrupted or may lose critical data, particularly when the user is moving around built-up areas. As a result, the user may not be satisfied with the displayed map and may transmit another request to the map server to alter the scale of the map. The process will be repeated until the displayed map meets the user""s satisfaction. However, this is tedious and time-consuming.
Therefore, there exists a need for eliminating the manual process of determining the scale of a map displayed on a wireless mobile terminal.
It is therefore an object of the present invention to provide a method and system for automatically displaying a map of appropriate scale on a mobile terminal.
The stated object is obtained by determining a degree of precision of estimated mobile position and determining the scale of a map according to the determined degree of precision.
According to a first aspect of the present invention, there is provided a method of displaying a map on a mobile terminal, comprising the steps of estimating a global position of the mobile terminal from signals transmitted from a plurality of GPS (global positioning system) satellites and received by the mobile terminal, determining a degree of precision of the estimated global position of the mobile terminal, determining a size of an area to be displayed according to the degree of precision, generating a map of the area of the determined size according to the global position of the mobile terminal, and displaying the map on the mobile terminal.
According to a second aspect, the present invention provides a mobile communication system comprising a communications network, a server connected to the network for estimating a global position from received GPS signals, and a mobile terminal for receiving GPS signals from GPS satellites and transmitting the received GPS signals to the server station via the communications network to cause the server station to determine the global position of the mobile terminal. The server determines a degree of precision of the estimated global position of the mobile terminal and determines the size of an area to be displayed on the mobile terminal according to the degree of precision, generates a map of the area of the determined size according to the global position of the mobile terminal and communicates the generated map to the mobile terminal.
According to a third aspect, the present invention provides a mobile communication system comprising a communications network, a mobile terminal for receiving GPS signals from GPS satellites, and a server. The mobile terminal estimates its global position from the received GPS signals, determines a degree of precision of the estimated global position of the mobile termial and determines the size of an area to be displayed on the mobile terminal according to the degree of precision. From the mobile terminal a server receives information as to the global position of the mobile terminal and the size of the map via the network, generates a map of the area of the size according to the received information and communicates the map to the mobile terminal via the network.